Embodiments of the invention generally relate to apparatus and methods of holding a substrate during processing. In particular, embodiments of the invention are directed to apparatus and methods using differential pressure to hold substrates on a susceptor under large acceleration forces.
In some CVD and ALD processing chambers, the substrates, also referred to herein as wafers, move relative to the precursor injector and heater assembly. If the motion creates acceleration forces larger than that of the frictional force, the wafer can become displaced causing damage or related issues. The wafers placed off-axis can slip at high acceleration/deceleration on a moving/rotating susceptor. Friction from the weight of the wafer itself is insufficient to hold the wafer on tools where higher throughput is desired.
To prevent the rotation forces from dislodging the wafer during process, additional hardware to clamp or chuck the wafer in place may be needed. The additional hardware can be expensive, difficult to install, difficult to use and/or cause damage to the wafers during use.
Therefore, there is a need in the art for methods and apparatus capable of keeping a wafer in position during processing to prevent accidental damage to the wafer and hardware.